WO1998030436A1

WO1998030436A1 - An apparatus for anchoring of a vessel and transfer of a floating load

Info

Publication number: WO1998030436A1
Application number: PCT/NO1998/000001
Authority: WO
Inventors: Carl K. Arnet; Kåre SYVERTSEN
Original assignee: Den Norske Stats Oljeselskap AS
Current assignee: Equinor ASA
Priority date: 1997-01-08
Filing date: 1998-01-07
Publication date: 1998-07-16
Anticipated expiration: 1999-07-08
Also published as: NO970071L; AU5579698A; NO970071D0

Abstract

An apparatus for anchoring of a vessel and transfer of a liquid load, such as oil, between an installation and tanks on the vessel (1), comprising a load-transferring device (5) which is rotatably mounted in a vertical shaft (3) extending from the bottom of the vessel (1) up to a space (4) in the vessel hull, the device at its lower end being connected to anchoring lines (14) for bottom anchoring of the vessel. The device consists of an essentially circularly cylindrical unit (5) which is permanently installed in the shaft (3) and constitutes or receives at least one load-transferring pipe (10), the lower end of the unit (5) being situated at a level with the bottom (11) of the vessel (1) and being provided with a connecting means (12) for interconnection between the at least one load-transferring pipe (10) and respective risers (6) from the installation, and the unit (5) at its upper end being provided with a connecting means (15) for connection of the at least one pipe (10) with the tanks of the vessel.

Description

AN APPARATUS FOR ANCHORING OF A VESSEL AND TRANSFER OF A FLOATING LOAD

The invention relates to an apparatus for anchoring of a vessel and transfer of a liquid load, such as oil, between an installation and tanks on the vessel, comprising a load-transferring device which is rotatably mounted in a vertical shaft extending from the bottom of the vessel up to a space in the vessel hull, the device at its lower end being connected to anchoring lines for bottom anchoring of the vessel.

An apparatus of the above-mentioned type is known from NO 164 968 (corresponding to DE 3 344 116). This known apparatus comprises a buoy arranged under an end of a ship and being connected to a vertical column projecting into the hull of the ship, a transfer line being passed through a central opening in the buoy and the column, the buoy forming a holder for bottom anchorings. The column is rotatably mounted in a sleeve in the hull, so that the ship can turn about the axis of the column. The column/buoy constitutes a relatively large body which is open at the bottom, so that the transfer line extends freely into the column/buoy opening and a distance up into the column space before the line is connected to a pipe fitted in the column space.

In connection with the transfer of a liquid load, such as oil, between a subsea installation and a floating vessel, the so-called STL system, wherein STL stands for "Submerged Turret Loading", has become widely accepted in the market. For a further description of this system there may, as an example, be referred to US patent No. 5 564 957.

In the STL system there is included a bottom-anchored, submerged buoy consisting of a central member having a through- going passage for medium to be transported via the buoy, and an outer buoyancy member which is rotatably mounted on the central member. The central member is provided with a lower, reinforced portion having a number of projecting arms for fastening of the anchoring lines of the buoy.

During operation, the STL buoy is received in a submerged receiving space in the hull of a tanker, and the outer buoyancy member of the buoy is locked in the receiving space. The vessel thereby is moored in a rotatable manner, the outer buoy member being rotatably mounted on the anchored central buoy member. At the lower end of the buoy a riser is connected to the lower end of the through-going passage of the buoy, and the upper end of the passage is connected to a pipe system leading to the storage tanks of the vessel. The connection takes place via a swivel device allowing said turning of the vessel about the central buoy member. Thus, the STL system allows a vessel to connect itself to the buoy in question, carry out the desired loading, disconnect itself from the buoy and the leave the loading site. The connecting and disconnecting operations can be carried out in a quick and safe manner, also under adverse weather conditions with relatively high waves, the STL buoy being introduced into and released from a submerged receiving space being at a relatively calm water depth.

The object of the invention is to provide an apparatus enabling anchoring of a tanker as a load-receiving terminal at an oil field with the utilization of parts of the well-proven and verified components of the STL-system, but where one has emancipated oneself from the use of the submerged STL buoy.

The above-mentioned object is achieved by means of an apparatus of the introductorily stated type which, according to the invention, is characterized in that the load-transferring device consists of an essentially circularly cylindrical unit which is permanently installed in the shaft and constitutes or receives at least one load-transferring pipe, the lower end of the unit being situated at a level with the bottom of the vessel and being provided with a connecting means for interconnection between the at least one load-transferring pipe and respective risers from the installation, and the unit at its upper end being provided with a connecting means for connection of the at least one pipe with the tanks of the vessel . Said unit may constitute a single load-transferring pipe, or it may receive several load-transferring pipes.

In the apparatus according to the invention the outer buoy member of the STL system is replaced by the hull of the vessel, the bearings for rotatable mounting of the central buoy member of the STL system being installed in the walls of the vertical shaft in the hull. This shaft receives the rotatably mounted unit which, at its lower end, is connected to the anchoring lines. The invention will be further described below in connection with exemplary embodiments with reference to the drawings, wherein

Fig. 1 shows a partly sectioned view of a part of a vessel which is equipped with an apparatus according to the invention, the section being shown in the central, vertical longitudinal plane of the vessel;

Fig. 2 shows a view corresponding to that of Fig. 1, of another embodiment of an apparatus according to the invention; Fig. 3 shows a segment of a ship hull, wherein an apparatus of a design similar to the apparatus in Fig. 1 is shown on an enlarged scale; and

Fig. 4 shows a corresponding hull segment to that of Fig. 3, but of a further embodiment of the apparatus according to the invention. in the various drawing Figures corresponding members and elements are designated by the same reference numeral .

As appears, the drawings show the forward part of a vessel 1 having a hull 2 in which there is provided a vertical shaft 3 extending from the bottom of the vessel up to a space or compartment 4 in the hull 2. In the shaft there is permanently installed a structure in the form of a rotatably mounted, essentially circularly cylindrical unit 5 serving as a load- transferring connection between one or more risers 6 and load- transferring equipment 7 (suggested in Figs. 3 and 4) fitted in the space 4 in the vessel. The unit 5 is supported and mounted by means of a radial bearing 8 fitted at the lower end of the shaft 3, and a combined axial and radial bearing 9 fitted at the upper end of the shaft.

The riser or risers 6 is/are associated with an installation (not shown) being at a distance from the vessel 1, whereas the load-transferring equipment 7, which is only symbolically shown in Figs. 3 and 4, communicates with tanks in the vessel 1, the vessel being presupposed to be a tanker.

The structure or unit 5, which serves as a load- transferring connection, comprises at least one pipe. The unit in Fig. 1 is shown to comprise one such pipe 10. As further appears, the lower end of the unit is terminated substantially flush with or at a level with the bottom 11 of the vessel 1, and s is provided with a connecting means for interconnection between the at least one load-transferring pipe 10 and an associated riser 6. In the embodiment of Figs. 1, 3 and 4 the connecting means comprises a flexible joint in the form of a spherical joint 12. At the lower end of the unit there are further provided o suitable holders 13 for anchoring lines 14.

In the embodiment shown in Fig. 1 the unit 5 as mentioned comprises a single pipe 10 for load transfer. This pipe extends centrally through the unit and at its upper end is provided with a swivel means 15 for connection to the load- s transferring equipment 7 in the space 4.

Figs. 3 and 4 also show embodiments comprising only one load-transferring pipe 10. However, in the embodiment of Fig. 3, the pipe itself is supported by the bearings 8 and 9 in the shaft 3, and in the embodiment of Fig. 4 the pipe 10 is received in a 0 sleeve-like member 16 which is supported by the bearings 8 and 9.

In Fig. 2 there is shown an embodiment wherein the unit 5 comprises a cylindrical shell structure 17 containing several pipes 18, each pipe 18 at its lower end being adapted for 5 connection to an associated riser 6. The pipes 18 are all at their upper ends provided with suitable connections for use together with the load-transferring equipment in the space 4. The connecting means are not further shown, but normally will comprise a multi-course swivel to allow turning of the vessel about the stationary, bottom-anchored unit 5.

In the embodiment of Fig. 1 the vessel suitably may be an FSO vessel, and the diameter of the unit 5 as an example may be ca 1,1 m. In the embodiment of Fig. 2 the vessel suitably may be an FPSO vessel, and the diameter of the unit 5 as an example may be ca 2,7 - 10 m.

As mentioned, the apparatus according to the invention is permanently installed in the topical vessel. In operation, the vessel is brought out to the place of use where already deployed anchors with anchoring lines are fastened to the lower end of the unit. Alternatively, the vessel may bring along parts of the anchoring/anchoring lines to the place of use, where an interconnection with the rest of the anchoring then is carried out. The number of risers corresponding to pipes in the unit thereafter is connected to the lower ends of the pipes. The apparatus therewith is ready for load transfer, as the upper ends of the pipes in advance will be connected to the pipe system which communicates with the tanks of the vessel.

Claims

P a e n t c l a i m s

1. An apparatus for anchoring of a vessel and transfer of a liquid load, such as oil, between an installation and tanks 0 on the vessel ( 1 ) , comprising a load-transferring device ( 5 ) which is rotatably mounted in a vertical shaft (3) extending from the bottom of the vessel ( 1 ) up to a space ( 4 ) in the vessel hull ( 2 ) , the device at its lower end being connected to anchoring lines (14) for bottom anchoring of the vessel, CHARACTERIZED IN s that the device consists of an essentially circularly cylindrical unit ( 5 ) which is permanently installed in the shaft ( 3 ) and constitutes or receives at least one load-transferring pipe (10; 18), the lower end of the unit (5) being situated at a level with the bottom (11) of the vessel (1) and being provided with a o connecting means ( 12 ) for interconnection between the at least one load-transferring pipe (10; 11) and respective risers (6) from the installation, and the unit (5) at its upper end being provided with a connecting means (15) for connection of the at least one pipe (10; 18) with the tanks of the vessel. 5

2. An apparatus according to claim 1, CHARACTERIZED IN that the unit (5) constitutes a single load-transferring pipe (10).

3. An apparatus according to claim 1, CHARACTERIZED IN that the unit (5) receives several load-transferring pipes (18). o

5